This invention relates generally to switches, and more particularly, to a connection arrangement for series-shunt surface mount radio frequency (RF) and microwave single pole, single throw (SPST) switches having a series PIN diode with a thermal conductor.
SPST solid state switches are commonly used for switching or steering RF power. For high average power (typically 10 watts (W) to 200 W continuous wave) and broadband RF applications (typically 1-1,000 MHz), P-type, Intrinsic, N-type (“PIN”) diodes in ceramic metal electrode leadless face (“MELF”) packages are often used for SPST switching. These MELF packages are used primarily due to low thermal resistance characteristics in both the die topology (i.e., device design) and the ceramic packaging. However, these MELF packages are not easily designed to include a heat transfer conduit that does not interfere with PIN diode anode (input) and cathode (output) electrical terminals, especially with respect to RF performance. Further, the PIN diode input and output electrical terminals connected to the circuit board typically have the lowest thermal resistance path relative to, for example, the ceramic MELF package body. Therefore, high average power PIN diodes used for SPST switches largely rely on the circuit board as the primary heat transfer conduit. This approach is not only not advantageous for circuit designers, but can affect circuit performance.
Other methods for heat dissipation in these packages are known. For example, use of an RF cover over the PIN diode in combination with a dielectric gasket under the PIN diode is known for dissipating heat. However, such an arrangement adds a capacitive loading effect to the circuit, which is undesirable. It is also known to use thermally conductive material in the gap traces between the anode and cathode of the PIN diode. However, a capacitive loading effect is again added to the circuit.
Thus, these known methods for heat dissipation can cause adverse effects to the overall system operation and affect system design. For example, these known heat dissipating methods can add undesirable capacitive loading as well as cause design constraints.